Cleaning device in electrophotography

ABSTRACT

A cleaning device for an electrophotographic copying apparatus comprising a photosensitive medium having liquid collection grooves formed at the opposite end portions thereof, and a cleaning blade of resilient material having an edge adapted to bear against the surface of the photosensitive medium. The cleaning blade has projections formed at the opposite ends thereof so that when the blade is brought to its cleaning position, the inner side walls of the projections thereof may keep liquid-tight contact with the inner side walls of the liquid collection grooves. Thus, relative sliding movement between the blade and the photosensitive medium removes any amount of developing liquid remaining of the surface of the photosensitive medium after an image transfer has been completed.

Saito et al.

Nov. 4, 1970 CLEANING DEVICE IN ELECTROPIIOTOGRAPIIY Inventors: TakashiSaito; Toshihide Iida,

both of Tokyo, Japan Assignee: Can on Kabushiki Kaisha, Tokyo,

Japan Filed: Nov. 2, 1971 Appl. No.: 194,956

Foreign Application Priority Data Japan 45/109363 l U.S. Cl 118/261,117/37 LE, 118/102, 118/104, 1l8/DlG. 23 Int.,Cl..;.. 603g 13/00Field'oi Search 117/37 LE; 118/100,

118/102, 104, 203, 261, 637, DIG. 23; 355/10, 15

1 References Cited UNITED STATES PATENTS 6/1968 Farrell 118/104 7/1952Govan 198/1 Sept. 18, 1973 2,889,758 6/1959 Bolton 355/15 X 3,667,4286/1972 Smith 118/637 3,368,566 2/1968 Matsumoto et al 1 18/637 3,552,8501/1971 Royka et a1 355/15 Primary Examiner-Mervin Stein AssistantExaminer-Leo Millstein Attorney-Joseph M. Fitzpatrick et al.

[57] ABSTRACT A cleaning device for an electrophotographic copyingapparatus comprising a photosensitive medium having liquid collectiongrooves formed at the opposite end portions thereof, and a cleaningblade of resilient material having an edge adapted to bear against thesurface of the photosensitive medium. The cleaning blade has projectionsformed at the opposite ends thereof so that when the blade is brought toits cleaning position, the inner side walls of the projections thereofmay keep liquid-tight contact with the inner side walls of the liquidcollection grooves. Thus, relative sliding movement between the bladeand the photosensitive medium removes any amount of developing liquidremaining of the surface of the photosensitive medium after an imagetransfer has been completed.

4 Claims, 9 Drawing Figures I CLEANING DEVICE IN ELECTROPIIOTOGRAIIIYBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to improvements in a cleaning device for a photosensitive mediumused with an electrophotographic copying apparatus of the liquiddevelopment and transfer type, and more particularly to a cleaningdevice using a cleaning blade to wipe a photosensitive medium to therebycollect and remove any amount of residual developing liquid from thesurface of the photosensitive medium.

2. Description of the Prior Art In the electrophotographic copyingapparatus of the liquid development and transfer type, the surface of aphotosensitive medium is wiped by a cleaning blade after image transfer,to gather the residual developing liquid near the blade, and then thedeveloping liquid flows laterally along the cleaning blade and downalong the periphery of the photosensitive medium at the opposite endsthereof or along grooves formed at such portions of the medium until itis collected for reuse.

The cleaning system of this type has often encountered a serious problemthat part of the developing liquid collected near the opposite ends ofthe cleaning blade may flow around these ends and leak to the surfacearea of the photosensitive medium which is located behindthe cleaningblade. If a subsequent electrophotographic process proceeds with suchleaking liquid still left on the surface of the photosensitive medium,no sufficient cleaning effect could be attained and stains or blotswould be formed in the next image reproduction. In addition, theinsulating characteristic of the surface of the photosensitive mediumwould be seriously reduced to attenuate electric charge and destroy theelectrostatic latent image on the surface of the photosensitive medium,thus adversely affecting the resulting image formation.

SUMMARY OF THE INVENTION An object of the present invention'is toeliminate the above-described troubles by employing a cleaning blade ofresilient material formed with projections at the opposite ends thereof,and a photosensitive medium formed with liquid collection groovesadjacent to the opposite ends thereof. The cleaning blade is installedin such a manner that the projections are received in the liquidcollection grooves of the photosensitive medium with the inner sidewalls of the projections kept in close or liquid-tight contact with theinner side walls of the grooves. By doing so, any amount of developingliquid remaining on the photosensitive medium may be interrupted by thecleaning blade and directed to flow toward the opposite ends of thephotosensitive medium, whereafter the liquid may flow along theprojections of the blade and further along the grooves on thephotosensitive medium for collection.

In the cleaning process as described above, the residual developingliquid on the photosensitive medium after image transfer may sometimesbe solidified due to a low content of carrier liquid therein. Also, someof the developing liquid may remain unremoved in or adjacent to the areaof contact between the photosensitive medium and the cleaning blade andsolidfy due to evaporation of the carrier liquid when the copyingapparatus is not in operation. Such solidified developer, i.e.,solidified toner, which intervenes between the blade and thephotosensitive medium, tends to injure the surface of the photosensitivemedium once a subsequent copying cycle is entered. This tendency is isespecially conspicuous at the beginning of the daily use of the copyingapparatus.

It is therefore another object of the present invention to solve such aparticular problem by designing the cleaning device so that exceptduring a cleaning cycle the cleaning blade is retracted into contactwith a body of carrier liquid so as to be kept wet with such liquid,thereby preventing the solidification of the developer and/or fixersticking to the blade, and that the blade is moved again into contactwith the photosensitive medium when a cleaning cycle starts. Means forretracting the cleaning blade away from the surface of thephotosensitive medium and maintaining it wet with the carrier liquid maybe of two alternative types, i.e., horizon tal movement type androtational movement type.

The above and other features of the present invention will become fullyapparent from the following detailed description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows anelectrophotographic copying apparatus of the liquid development andtransfer type in which the cleaning device of the present invention isincorporated.

FIG. 2 is a perspective view of an embodiment of the photosensitivemedium according to the present invention with the conventional cleaningblade applied thereto.

FIG. 3 shows an improved cleaning blade according to the presentinvention.

FIG. 4 is a perspective view of a photosensitive medium with thecleaning blade of FIG. 3 applied thereto.

FIG. 5 is a fragmentary perspective view showing another embodiment ofthe present invention.

FIGS. 6 and 7 are a cross-sectional view and a plan view, respectively,of an embodiment of the cleaning device in which the cleaning blade isrotatable to move into a carrier liquid reservoir.

FIGS. 8 and 9 show further embodiments of the present invention.

DESCRIPTIONOF THE PREFERRED EMBODIMENTS In order to eliminate thedisadvantages described previously, the cleaning blade used with thecopying apparatus as shown in FIG. 1 may preferably take the form asshown in FIG. 3, instead of the conventional form shown in FIG. 2. InFIG. 1, which shows a drum type electrophotographic copying machineincluding a drum type photosensitive medium 1 rotatable in the directionof arrow, primary charger 13, AC (or DC) corona discharger 14, lightimage exposure means 15, whole surface exposure means 17, liquid typedeveloping means 116, post charger l8 and transfer means 21 and so onare arranged. In FIG. 1, the liquid type developing means 16 is shown,together with a blade type cleaning means 26. The developing liquid in atank 12 may be utilized as cleaning liquid. When the main switch (notshown) is closed, a drive source 8 is energized to supply the developingliquid from the tank and centrifugal pump 11 or the like throughdistributor means 9 into a pipe terminating at a spray conduit 10,through which the developing liquid is applied to blade means 26 and tothe surface of the photosensitive medium. The conventional blade meanscomprises a blade 24, as shown in FIG. 2. In this case, a part of thedeveloping liquid collected near the opposite ends of the cleaning blademay flow around these ends and leak to the surface area of thephotosensitive medium which is located behind the cleaning blade, whichcauses stains or blots in the next image reproduction. The cleaningblade 2 shown in FIG. 3 is formed of resilient material and hasprojections 2' formed at the opposite ends thereof. Where such acleaning blade is to be used with a drum type photosensitive medium 1 asshown in FIG. 4, developing liquid collection grooves 3 are formed alongthe periphery of the drum adjacent to the opposite ends thereof and thecleaning blade 2 is mounted with its projections 2' received in therespective collection grooves 3. In this case, it is essential that theinner side wall of each projection 2' of the cleaning blade 2 shoud bein close contact with the inner side wall 4 of each collection groove 3.When the photosensitive drum 1 is rotated in the direction indicated bya curved arrow in FIG. 4, developing liquid flowing in the directionsindicated by arrows 5 will be interrupted by the cleaning blade 2 anddirected toward the opposite ends of the photosensitive drum 1 so thatthe liquid will further flow along the projections 2 of the blade 2 andinto' the grooves 3 for collection, as indicated by arrows FIG. 5 showsan alternative form of the cleaning blade according to the presentinvention. As shown there, the cleaning blade 2 has no integralprojection 2' but instead, employs separate guide members 7, only one ofwhich is shown. The guide members 7 may be disposed at each end of thecleaning blade 2 in such a manner as to kee close contact with thesurface of the blade 2 and with the inner side wall of the collectiongroove 3. With this arrangement, the developing liquid may beinterrupted by the cleaning blade.2 and directed into the collectiongrooves 3 formed at the opposite ends of the photosensitive drum 1,whereby the developing liquid remaining on the surface of thephotosensitive medium may be completely prevented from flowing past theblade to the surface area of the photosensitive medium which is locatedbehind the cleaning blade.

FIGS. 6 and 7 show a device of the type in which the cleaning bladedescribed above is maintained wet in a carrier liquid reservoir duringthe suspension of the cleaning operation. The cleaning blade used inthis device is of the type which is rotatable to move between thephotosensitive medium and the carrier liquid reservoir. In FIGS. 6 and7, the photosensitive medium 1 is formed with developing liquidcollection grooves 3 similar to those shown in FIGS. 4 and 5, and theblade 2 is formed of rubber such as NBR or the like having a highoil-resistivity. The blade 2 is supported by a blade holder 25 attachedto a torque tube 28. The torque tube 28 is rotatably mounted on a shaft30 which extends between and is secured to a frame 29. The torque tube28 carries a pulley 31 at one end thereof. A spiral spring 32 isprovided between the shaft 30 and the pulley 31 to bias the pulley 31,torque tube 28 and blade 2 in clockwise direction and thereby hold theblade 2 in the position as shown by imaginary lines in FIG. 6.

A wetting means, generally designated by numeral 33, is provided toprevent the blade 2 from drying up. The wetting means comprises areservoir 35 filled with a body of developer carrier liquid 34 such askerosene and a supply tank 36 for supplying such liquid to maintain theliquid in the reservoir 35 at a constant level. The supply tank 36 isinterchangeable and may be of the chicken feed type. The reservoir 35 isformed with an opening 37 through which the blade 2 may pass into thecarrier liquid 34 in the reservoir 35. Although not shown, a coverresponsive to the movement of the blade 2 may be provided to close theopening 37 during a cleaning cycle. A motor 38 is provided to drive thetorque tube 28 and blade 2 via belt 39 and pulley 31. The motor maystart in response to the closing of an unshown power switch of thecopying apparatus and stop in response to a signal from an unshownmicroswitch.

There are further provided electromagnets 40 which may be energized uponclosing of the power switch of the copying apparatus to attract members41 attached to the torque tube 28 when the blade 2 is brought to itscleaning position.

In operation, the power switch (not shown) of the copying apparatus isfirst closed to start the motor 38 and energize the electromagnets 40 atthe same time. The motor 38 drives the belt 39 and pulley 31 to rotatethe torque tube 28 and blade 2 counter-clockwise about the shaft 30against the force of the spiral spring 32 so that the free end of theblade 2 comes out of the carrier liquid 34 in the wetting means 33 toapproach the surface of the photosensitive medium 1. Thereupon, theenergized electromagnets 40 attract the members 41 of the torque tube 28so that the free end of the blade 2 resiliently bears against thesurface of the photosensitive medium 1 to assume its cleaning position(FIGS. 6 and 7). Thereupon, the microswitch is opened to stop the motor38 and wind up the spiral spring 32. When the power switch of thecopying apparatus is opened after completion of a copying operation, theelectromagnets 40 are deenergized to allow the blade 2 to be rotatedclockwise by the return force of the spiral spring 32 until brought backto the opening 37 of the wetting means 33 and dipped in the carrierliquid therein. Thereupon, the microswitch is closed to enable the motor38 to be energized at the initiation of the next copying cycle (seebroken-line position in FIG. 6).

FIG. 8 shows another form of the mechanism for moving the cleaning bladein response to the closing of the power switch of the copying apparatus.As shown, a slide switch 42 and a pulley 43 are connected by a wire 44.From a pulley 45 mounted on a shaft common with the pulley 43, via apulley 46 to a pulley 47, there extends a further wire 48. The pulley 47is securely mounted on the torque tube 28 having the plate holder 25attached thereto. With this arrangement, displacement of the switch 42in the direction of arrow ON" may be utilized to rotate the blade 2 inthe counterclockwise direction so as to assume its cleaning position forapplying a predetermined cleaning pressure to the surface of thephotosensitive medium with the aid of the return force of a spring (notshown) provided between the shaft 30 and the torque tube 28. Thereafter,upon completion of a copying cycle, the switch 42 may be moved in thedirection of arrow OFF" to return the blade 2 into the wetting means 33,whereafter the blade 2 may be maintained in that position as by clipmeans (not shown).

Instead of the slide switch, use may be made of any lever switch whichcan provide an amount of displacement. Also, means'for moving the blade2 is not limited to the shown pulley-wire system but the principle oflever motion may be utilized for the same purpose.

FIG. 9 shows a further embodiment of the cleaning device in which thecleaning blade 2 is adapted for horizontal movement. Upon completion ofa copying cycle, the blade 2 may be moved horizontally from its cleaningposition (solid-line position) to a scraper plate 50 for removingmaterial 49 such as toner, fixer, etc., sticking to the free end of theblade 2. Thereafter, the blade 2 may rest on a pad 51 which isimpregnated with carrier liquid 34, whereby the blade may be maintainedwet with such liquid. The reservoir 35 of the wetting means 33 has acarrier liquid supply port 52. Although the mechanism for accomplishingthe described horizontal movement of the blade 2 is not shown, suchmechanism may be provided as by connecting the blade holder 25 through arack-pinioq system to a drive source which is operable in a mannersimilar to the motor 38 shown in FIGS. 6 and 7.

Thus, according to the present invention, the cleaning blade is incontact with the surface of the photosensitive medium only during acleaning cycle and, after completion of a copying cycle, the blade isseparated from the surface of the photosensitive medium and maintainedin wet condition so that any amount of toner and/or fixer sticking tothe blade and existing between the blade and the surface of thephotosensitive medium may be prevented from solidifying to injure theblade and/or the photosensitive medium during a subsequent operation.

We claim:

1. A cleaning device for an electrophotographic apparatus including aphotosensitive medium, comprising means defining liquid collectiongrooves at the opposite end portions of said photosensitive medium, anda cleaning blade of resilient material having an edge adapted to bearagainst the photosensitive medium, said cleaning blade havingprojections formed at the opposite ends thereof so that the inner sidewalls of said projections may keep liquid-tight contact with the innerside walls of said liquid collection grooves, whereby relative slidingmovement between said blade and said photosensitive medium removes anyamount of developing liquid remaining on said photosensitive mediumafter an image transfer has been done,

2 A cleaning device as defined in claim 1, wherein said projections ofsaid cleaning blade comprise guide members attached to the blade.

3. A cleaning device as defined in claim ll, further comprising meansfor moving said cleaning blade from the surface of said photosensitivemedium into a carrier liquid reservoir to maintain said blade in wetcondition during the suspension of cleaning operation.

4. A cleaning device as defined in claim 1, further comprising means fororienting said cleaning blade in a counter direction with respect to thedirection of movement of said photosensitive medium.

1. A cleaning device for an electrophotographic apparatus including aphotosensitive medium, comprising means defining liquid collectiongrooves at the opposite end portions of said photosensitive medium, anda cleaning blade of resilient material having an edge adapted to bearagainst the photosensitive medium, said cleaning blade havingprojections formed at the opposite ends thereof so that the inner sidewalls of said projections may keep liquid-tight contact with the innerside walls of said liquid collection grooves, whereby relative slidingmovement between said blade and said photosensitive medium removes anyamount of developing liquid remaining on said photosensitive mediumafter an image transfer has been done. CM,2Aning device as defined inclaim 1, wherein said projections of said cleaning blade comprise guidemembers attached to the blade.
 3. A cleaning device as defined in claim1, further comprising means for moving said cleaning blade from thesurface of said photosensitive medium into a carrier liquid reservoir tomaintain said blade in wet condition during the suspension of cleaningoperation.
 4. A cleaning device as defined in claim 1, furthercomprising means for orienting said cleaning blade in a counterdirection with respect to the direction of movement of saidphotosensitive medium.